1. Field of the Invention
The present invention relates to a method for the underground installation of pipelines, which preferably have impassable cross sections, by driving pipe sections into the ground, with the earth at the driving face being loosened by being broken up, pulverized, or bored by means of a liquid jet ejected or discharged from a nozzle head at high pressure and high speed; the excess earth is transported backwards from a removal zone between the driving face and a removal device through the pipe for removal or treatment. The present invention also relates to an apparatus for implementing such a method. The apparatus has at least one driving unit for the pipe, and a machine unit which is traversable in the pipe and has at least one nozzle head for loosening the ground; the machine unit is connected by piping to supply and removal units and by cables to control devices, and has at least one removal pipe for conveying away the loosened earth.
2. Description of the Prior Art
The construction of pipelines having small, impassable cross-sectional diameters by the known driving method is finding increasing application. Starting from a driving station, pipe sections are driven forward by being pushed into the ground, with the earth at the head of the driving line being loosened by means of suitable machine units and being conveyed through the interior of the pipe to the access shaft, and from there to the earth's surface. The known methods for the construction of impassable pipelines are essentially capable of being steered, so that a certain directional accuracy can be adhered to.
The systems mentioned below for the installation of such pipelines are known, and to some extent have already been tried out in practice. In a Japanese system, known by the name Tele-Mole or Tele-Mouse, the machine unit for loosening the earth consists essentially of a boring head with a drive, and a shield unit, which are not separable and are driven into the ground ahead of the actual pipe sections and with the latter. The machine unit cannot be retracted through the driving line during the advance. A separate machine unit must be used for each different external pipe diameter.
A so-called horizontal boring device is also known, with which diameter ranges from 700 to 1000 mm can be driven with the same boring head drive. Only the boring head and the steel sleeve of the boring device have to be adjusted to the external diameter of the pipe. However, this boring device is also not retrievable through the driving line during driving.
Whereas with the heretofore known systems a steerable boring device with a boring head or a digging plate digs out the external diameter of the pipe directly in the ground, the so-called Iron Mole System works on the so-called widening principle. In this case, a steerable pilot head of small cross section on a tubular steel pipe, the so-called pilot pipe, is first driven up to the target shaft. This pilot bore-hole is then widened by means of a so-called widening stage to the final external diameter. In this case, the pilot pipe is recovered in sections in the target shaft. The system is suitable for external pipe diameters of 216 to 730 mm.
In the field of construction of impassable pipeline cross sections, the Hansemole System, a further development of the Tele-Mole System, is known as a more recent development. By means of a conical design of the digging plate, the external diameter of the pipe is supposed to be overlapped, and too-coarse grain forced outwards. At the same time, stones with a diameter of 13 to 15 cm are supposed to be fed inside to an incorporated crusher. A further development of the hydraulic shield for large diameters is the hydraulic jet shield, which has been specially developed for smaller diameters. Inside the shield sleeve the earth is loosened by jets directed towards the axis, and is pumped away. The hydraulic jet shield cannot, however, be retrieved during the driving operation.
Another known device uses a steel pipe articulated shield. In this system there are also two pipes driven instead of one. The overall construction time is therefore long, and the number of machine pipe elements held available for the various diameters is large. The steel pipe articulated shield does, however, offer the possibility of recovering the boring head and the boring drive at any point in the driving operation for the purpose of repair or maintenance work.
A further known driving system operates with exchangeable working tools. All of the working tools and drives are housed in a so-called inner shield which can be pulled back to the access shaft through the already driven pipeline on runners or wheels by means of steel cables.
All the above-mentioned driving systems for impassable pipelines are limited in their field of use, especially by the ground strength and the receivable maximum grain, the diameter of which, measured on the longer side, must not exceed 80 to 130 mm. In addition, it is generally necessary to use gravel crushers which pulverize the large grain from 80 to 130 mm down to about 20 to 30 mm, in order that the latter can be transported out by means of the hydraulic coveyer. None of the systems mentioned is capable of combining and satisfying all the requirements associated with the underground driving of pipelines having impassable cross sections between about 300 to about 1000 mm, and with the loosening process involving removal. These requirements are summarized as follows: During driving there must be the possibility of continuous positional measurement and directional correction of the driving line. The device must enable a depth-independent, low-settlement application in as many grounds as possible without ground-water lowering, and it must not be susceptible to failure in the presence of fairly large earth inclusions and obstructions in the pipe route. The machine unit must be able to be recovered at any time during the driving operation for the purpose of repair, maintenance, and the replacement or exchange of tools and machines. The units for loosening and transporting the earth should be mechanically rugged and simply require little maintenance and not be susceptible to repairs. Moreover, the device should be suitable for as wide a range as possible of inner and outer diameters of the pipeline, and should require only low investment and operating costs and the storage in stock of only a few system components. The pipeline should be statically secured. Finally, the device should have a high operating efficiency due to high driving speeds, and no double casing should be necessary.
It is an object of the present invention to provide a method and an apparatus with which it is possible to satisfy the above-mentioned requirements which have to be imposed on a steerable drive.